Orthodontic pliers which include two separable parts are well known. Each one of two parts has a handle and some type of jaw device. The parts are joined by a hinge which must be disassembled to separate the parts. The ultimate objective is to provide a strong and reliable pliers construction which wears well, and whose parts are amenable to simple cleaning and sterilization procedures. Uncomplicated procedures and physical arrangements for hinge separation are much to be preferred.
Examples of known separable pliers are Fowler III U.S. Pat. No. 5,197,879 and Ingels U.S. Pat. No. 5,232,360. The Fowler pliers illustrate the problems when a pinless hinge is used. It relies on a dovetail arrangement that holds the parts together throughout a pre-established amount of opening of the handles and jaws. Beyond that limit, the parts fall apart from one another. Either some releasable means must be provided to limit this movement, or care must be taken by the user to prevent movement beyond the limit. The relatively short dovetail surfaces take the wear caused by squeezing of the handles together. Ultimately this wear will cause undesirable sloppiness of action, or some adjustment means must be provided.
The Ingels patent provides a hinge that has a pin and a recess which both center the parts and take the wear over a substantial area. The parts are prevented from separating by overhanging shoulders of limited extent, and readily separate when their handles are separated beyond this extent, but are held by an extra spring.
It is an object of this invention to provide a separable pliers in which the separation of the handles is limited by the same spring which biases the handle apart. This provides a pliers which is reliably held together and which can readily be disassembled by the simple deflection of the spring.